EU foreign ministers voiced concern at developments in Syria on Thursday, calling for a renewal of UN-led efforts to end the conflict.

The European Union will host a conference on the future of Syria in Brussels next month aimed at mobilising humanitarian support for Syrians both inside and outside the country.

French Foreign Minister Jean-Yves Le Drian said UN peace talks should restart "as soon as possible" and called for UN special envoy Staffan de Mistura to have his mandate "reinforced".

"We had a civil war and now there is a risk of a major regional crisis," Le Drian told reporters at talks between EU foreign ministers in Sofia.

The EU's diplomatic chief Federica Mogherini said the bloc would try to use its influence to support the UN process, which has included eight rounds of talks in Geneva during which the two sides failed to even meet each other.

"The humanitarian situation is still a dramatic one and we aim at mobilising humanitarian support for Syrians both inside the country and in the neighbouring countries -- namely in Jordan, Lebanon and Turkey," Mogherini said.

German Foreign Minister Sigmar Gabriel said that as well as giving a push to the peace process, the EU should also "ensure... the military escalation is halted in northern Syria."

Turkey last month launched an operation in northern Syria against the Syrian People's Protection Units (YPG), which Ankara blacklists as a Kurdish terror group but which is closely allied with the US in the battle against jihadists.